Chap. 6. 



INVERTEBRAL ANIMALS OF VERMONT. 



159 



FRT'.SH watp:r and land shells. 



in lake Champlain, it is abundant, in com- 

 pany with Saccinra oliliqua. The reddish 

 variety is rare. Tiie size of mature speci- 

 mens is sometimes less than an inch in 

 their greatest diameter. During the day, 

 except in damp weather, tlie\' are confined 

 to their retreats under logs and stones. 

 Tlieireggs are white, nearly globular, and 

 about U.2 inch in diameter. The young 

 shell does not receive the reflected lip 

 until of its full size. 



Helix thyroidus. — Say. 



Description. -Shell globose-conic, with 

 a light brown, sometimes reddish epider- 

 mis, with five parallel oblique incremen- 

 tal striEB ; wliorjs five, conve.v, with a well 

 impressed sutare ; aperture contracted by 

 the labrum, which is widely reflected, 

 flat, white, next the aperture, yellowish 

 externally ; inner margin with an oblique 

 tooth ; umbilicus partly covered by the 

 reflected labrum, exhibiting only one vo- 

 lution. Greatest breadth O.t'-'S inch ; least 

 breadth 0.7 inch ; height 0.'17 inch ; di- 

 vergence 140°. 



Remarks. — This species is extremely 

 rare in Vermont, but is more common in 

 the western states. It might, at first, be 

 confounded with the preceding, but is 

 distinguished by the tooth on the inner 

 margin of the aperture, the partially open 

 umbilicus, and the yellow color of the 

 outside of the labrum. 



Helix dentifcra. — Binney. 



Description. — Shell depressed, with a 

 yellowish horn-colored epidermis, with 

 fine parallel oblique incremental striae ; 

 whorls five, with the suture distinct but 

 not deep ; aperture contracted by the lip, 

 which is white, and broadly reflected ; 

 inner lip with a large tooth, long and par- 

 allel with the lovi'er margin; umbilicus 

 none. Greatest breadth 0.9 inch ; least 

 breadth 0.6 inch ; height 0.44 inch ; di- 

 vergence 13.5". 



Remarks. — This very rare species has 

 been found only by Dr. Binney on the 

 east side of the Green Mountains. 



Helix ■palliata. — Say. 

 Description. — Shell depressed, with a 

 dark reddish brown epidermis, which is 

 thickly covered, when in a perfect state 

 of preservation, with acute hair-like pro- 

 jections ; with numerous fine oblique in- 

 cremental strite; whorls five, flattened, 

 with a distinct suture; aperture much 

 contracted and made three- lobed by the 

 teeth ; labrum white and broadly reflect- 

 ed ; teeth three, of which one is long and 

 curved, nearly covering the pillar lip ; 

 two are on the inner margin of the la- 

 brum; one above is acute and prominent. 



and the other below is long and lamellar; 

 the labrum is continued over the umbili- 

 cal region in a white callus. Greatest 

 breadth 0.9 inch ; least breadth 0.6 inch ; 

 height 0.48 inch ; divergence about 160°. 

 Remarks. — Tliis species, which is not 

 rare in the western states, is seldom found 

 in Vermont. It is easily distinguished 

 from H. tridentuta by the want of an um- 

 bilicus. 



Helix monodon. — Rackett. 



Description. -Shell globose-conic, with 

 a brown hirsute epidermis, with minute 

 incremental strife; whorls six, with a dis- 

 tinct suture ; aperture contracted by a 

 deep groove behind the tip, which is 

 white, reflected, flattened, covering more 

 or less of the umbilicus, which is deep 

 but not wide ; inner lip with a compress- 

 ed elongated tooth, parallel with the low- 

 er part of the margin. Greatest breadth 

 0.45 inch; least breadth 0.42 inch; height 

 0.26 inch ; divergence 135°. 



Remarks. — In this description we have 

 included //. fni/rnio^ Say, a variety in 

 which the umbilicus is entirely covered 

 by the labrum. As this is a variable char- 

 acter, and the other characters present no 

 distinction, we cannot separate them. 

 Rackett's name has the priority both of 

 Say's description of the variety and of 

 Ferussac's use of the same name for an- 

 other species. This is common on hill 

 sides in rather dry places. Specimens 

 vary in respect of size and the elevation 

 of the spire. 



Helix concnva. — Say. 



Description. — Shell depressed, a little 

 convex above, v/ith fine oblique incre- 

 mental striae ; epidermis pale greenish 

 horn color ; whorls five, flattened above, 

 elegantly rounded below, the outer one 

 dilating towards the ajjerture, with a well 

 impressed suture ; labrum partially re- 

 flected below, simple above ; inner lip 

 with a thin callus, which connects the ex- 

 tremes of the labrum; umbilicus wide 

 and deep, exhibiting all the volutions. 

 Greatest breadth 0.75 inch ; least breadth 

 0.6 inch ; height 0.33 inch ; divergence 

 about 155°. 



Remarks. — This species is rare in Ver- 

 mont, but more common in the western 

 states. West of the Rocky Mountains it 

 is of a much greater size, exceeding an 

 inch in diameter. 



Hdix piiMclh.—MvLL. 

 Description. — Shell much depressed, 

 pale horn color, nearly transparent, finely 

 striate, with a colorless epidermis ; whorl.s 

 three and a half, convex, with a deep su- 

 ture, the last oxie much larger tU.an tho 



